Pests & Problems
Tired of combating pests and problems in your garden?
In this page I help you identify pests, get to know their habits and the methods you can use to control them.
I also provide solutions to common problems that plague most gardens.
Order: Hemiptera Sub-Order: Homoptera
Anyone who grows roses will be familiar with aphids. They are a pest with sucking mouth-parts that are attracted to the soft growth in Spring, which enables them to probe easily into the plant vessels and feast on the sugary liquid within. This can weaken your plants and result in poor, distorted growth with less resistance to disease. They also act as vectors of viral plant diseases, injecting virus particles with saliva into the host plant.
They are a fascinating insect, in that they can produce live young by parthenogenesis. That is, the females can produce young that are exact copies of themselves, without fertilisation. This allows aphids to produce many young when the season is favourable.
The average aphid is 1-2 mm long and can be green, brown, whiteish, black, pinkish or yellow. They have a large abdomen, can have wings, are very sluggish movers and produce globules of honeydew from cornicles at the rear of the abdomen. Honeydew is very attractive to ants, who will farm aphids to get that sugary sweet. Black mould will also grow on honeydew left on the leaves and this is often a problem in Citrus. There are different types of aphids that will infest peaches, tomatoes, melons, cabbages, citrus, roses and many more.
Although aphids can damage your plants, the best way to get them under control is to follow the way of nature. The control method used to be, reach for the insecticide and go mad. However, we now understand that the natural predators of aphids are out there in your garden, waiting for numbers to build up before they pounce. They need aphids for food and will greatly reduce their numbers if left to do their job. Using sprays will remove their food source, and may even kill the good predators. This can result in even more of an aphid problem later, if predator numbers are reduced.
So, remove some pests if necessary if your plants are suffering, but leave the rest for ladybirds, wasps, hoverflies and lacewings. Remove infested weed hosts such as thistles and any harvested vegetable plants that may harbour aphids, and use a jet of water to wash off thick infestations. Look for the small brown lumps on leaves, and if you see a tiny hole in the top you will know that the parasitic wasps have been at work and to leave the rest of the aphids alone.
Water Repellent Soil
Water repellent soils are a big problem throughout the world especially in dry countries like Australia. If you have such a soil, you can water it for hours and think that the moisture has penetrated. Often the surface looks wet, but water has only penetrated the first millimetre of soil. Wipe your finger over the surface and you’ll see underneath is as dry as dust. Most of the water has just run off and the plant roots are still thirsty. In some soils you will also notice water just beads and sits on the surface without even penetrating.
Good soils with plenty of organic matter and having an open crumbly texture don’t often become water repellent, especially if you water regularly. The two major reasons for developing repellency are the type of soil and neglect. Repellency develops when soil particles become coated with a waxy substance which sheds water very quickly. The trick is, to break down this substance.
Type of Soil
You should always find out what type of soil you have in your garden. My book Know Your Soil will help you with this.
Sandy soils are likely to repel water and these are known as hydrophobic (fear of water) soils. They occur naturally and if you have one of these you will need to take steps to change it. The best way is to introduce well composted organic matter. Not mountains of it, but enough to change soil texture, then repeat with a little every few months. This works because organic matter contains plenty of soil microbes and they work to break down the wax coating. Organic matter also absorbs moisture, so when you water, it holds it in the soil.
You can also add soil wetting agents which are sold in granular and liquid forms. These are good if you want an instant fix but be wary of using them on a vegetable garden as some may be made with strong chemical agents.They also need repeated applications.A review of wetting agents will be appearing on my Plants & Products page soon.
If you allow your soil to dry out repeatedly, compact it by walking or driving over it or leave it open to the elements, it can become water repellent. Drying out and compaction, especially with clay type soils, will allow a hard crust to form on top which is like a layer of lacquer. Water will not easily penetrate. The steps you must take is to incorporate organic matter as above, put on a layer of mulch (3 cm) and water regularly. This type of neglect will also allow a waxy coating to form on soil particles.